Floods in Dinaric Karst fields: a case study of the Dicmanjsko-Bisko Polje (Croatia)

Abstract

ABSTRACT Karst areas are characterized by extreme heterogeneity and variability of geologic, morphologic, hydrogeologic, hydrologic, hydraulic, ecologic and other parameters in space and time. Therefore, the occurrence of floods under such condition manifests in different forms, intensities, and durations. Heavy precipitation in karst areas leads to a considerable increase in groundwater levels and the activation of temporary springs. Karst fields that have not been properly meliorated are particularly vulnerable to such phenomena and, can remain flooded for several weeks. In Dalmatia, in the southern Croatian region, there are 12 karst poljes with an area larger than 1000 ha, including Dicmanjsko-Bisko polje (1700 ha). Our study presents a conceptual model of the interaction of underground and surface water in the Dicmanjsko-Bisko polje, as well as the process of flooding. The input data were geological mapping and measured precipitation. The paper describes the December 2021 flood in detail. The average 11-day precipitation recorded in the field catchment area was 292 mm, which led to the flooding of 230 ha (approximately 14% of the field area). The main cause of the flooding in the western part of the field was a large amount of surface runoff, resulting in insufficient capacity of the existing drainage channels. In the eastern lowest part of the field, flooding was even more intense due to the insufficient capacity of the sinkhole. The flood caused damage to agricultural lands, infrastructure, and economic facilities. The paper proposes flood mitigation measures. The study is an example of the practical application of karst research, that can be used for different purposes (spatial planning, hydrologic monitoring, modeling hydrogeological processes).